Ball check valve molten metal injector

ABSTRACT

The injector includes a cylinder defining a piston cavity housing a reciprocating piston for pumping molten metal from a holder furnace and injecting the molten metal into the mold cavity of a casting mold. The piston defines a molten metal intake for receiving molten metal into the piston cavity. A check valve is positioned in the molten metal intake defmed by the piston. The check valve is preferably a ball check valve. The cylinder further defines a fill conduit in fluid communication with the piston cavity. The fill conduit extends through a top wall of the cylinder and extends along an axis substantially parallel to the piston.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of U.S. application Ser. No. 09/630,781, filed Aug. 2, 2000, entitled “Ball Check Valve Molten Metal Injector System”, which claims the benefit of U.S. Provisional Application Serial No. 60/146,827, filed Aug. 2, 1999, entitled “Ball Check Valve Metal Injector System”.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH

[0002] The subject matter of this application was made with United States government support under Contract No. 86X-SU545C awarded by the Department of Energy. The United States government has certain rights to this invention.

Background of the Invention

[0003] 1. Field of the Invention

[0004] The present invention relates to a casting apparatus for producing ultra large, thin-walled components and, in particular, to a molten metal injector system for producing ultra large, thin-walled components that includes an injector having a check valve incorporated into the pumping mechanism of the injector.

[0005] 2. Description of the Prior Art

[0006] The manufacturers of ground transportation vehicles, such as automobiles, sport utility vehicles, light trucks, vans, buses and larger capacity trucks, have made major efforts in recent years to reduce vehicle weight. Weight reductions reduce harmful atmospheric emissions and increase fuel efficiency of ground transportation vehicles. Presently, a majority of the body components for ground transportation vehicles are formed from individual steel components assembled via resistance spot welding. For example, the floor pan frame of an automobile is normally constructed from a number of individual steel stampings that are spot welded together. It would be advantageous to produce body components for ground transportation vehicles, such as the floor pan frame of an automobile, as a single, ultra large casting. As a result, the costs associated with producing multiple steel stampings and then assembling the stampings would be eliminated. The same technology would also be suitable for producing components in the aerospace industry.

[0007] There are several known methods for producing thin-walled castings. Examples include: high pressure cold chamber vacuum die casting, premium sand casting, a level pour process practiced by Alcoa, Inc. for producing components for the aerospace industry, and low-pressure hot chamber injection. Low-pressure hot chamber injection is particularly well suited for producing components made from non-ferrous metals having a low melting point, such as aluminum, brass, bronze, magnesium and zinc.

[0008] Several arrangements are known in the prior art for casting molten metal in a casting mold. In particular, arrangements are known in the prior art, which incorporate a check valve to prevent molten metal backflow out of the mold cavity of the casting mold. For example, U.S. Pat. No. 4,862,945 to Greanias et al. (hereinafter “the Greanias patent”) discloses an apparatus for vacuum counter-gravity casting of molten metal that includes a casting mold defining a mold cavity. The arrangement disclosed by the Greanias patent includes a ball check valve positioned in a passage leading to the mold cavity for preventing backflow of molten metal from the mold cavity. U.S. Pat. No. 5,244,033 to Ueno discloses a die casting apparatus, which incorporates ball check valves in a passage leading to a storage tank for preventing molten metal from flowing backward to the storage tank after injection of the molten metal into a mold cavity of the apparatus. Similarly, U.S. Pat. No. 5,657,812 to Walter et al. discloses a metal casting apparatus utilizing a check valve in a passage leading from a supply tank to a mold cavity for preventing backflow of molten metal from the mold cavity to the supply tank. However, none of the foregoing devices known in the prior art incorporates a check valve device directly into the pumping mechanism of the device.

[0009] Accordingly, it is an object of the present invention to provide a molten metal injector for use with a molten metal injector system adapted to cast inexpensive, but high quality, thin-walled components. In addition, it is an object of the present invention to provide a molten metal injector for use with a molten metal injector system adapted to cast thin-walled components of such size and complexity that traditional stamping assemblies made from multiple stamped components could be replaced with a single, thin-walled component. It is a further object of the present invention to provide a molten metal injector for use with a molten metal injector system that provides high quality cast products by reducing or eliminating the introduction of undesirable metal oxides and/or air bubbles in a casting mold when molten metal is injected into the casting mold.

SUMMARY OF THE INVENTION

[0010] The above objects are accomplished with a molten metal injector system according to the present invention. The present invention combines the advantages known with low-pressure hot chamber injection with an improved injector which incorporates a check valve into the pumping mechanism of the injector resulting in significant improvements over known casting arrangements and injectors. The molten metal injector system of the present invention includes a holder furnace for containing a supply of molten metal having a metal oxide film surface. A casting mold is supported above the holder furnace and has a bottom side facing the holder furnace. The mold defines a mold cavity for receiving the molten metal from the holder furnace. A molten metal injector is supported from the bottom side of the mold and projects into the holder furnace. The injector is in fluid communication with the mold cavity and includes a piston positioned within a piston cavity defined by a cylinder for pumping the molten metal upward from the holder furnace and injecting the molten metal into the mold cavity under pressure. The cylinder is at least partially submerged in the molten metal when the holder furnace contains the molten metal. The piston defines a molten metal intake for receiving the molten metal into the piston cavity. A check valve is preferably positioned in the molten metal intake defined by the piston. The check valve may include an inlet for receiving the molten metal into the piston cavity. A molten metal filter may be used to cover the inlet to the check valve for filtering the molten metal flowing into the piston cavity through the check valve. The check valve may be a ball check valve.

[0011] The piston may be oriented substantially perpendicular to the bottom side of the mold and movable through a downstroke and a return stroke During the downstroke of the piston, the check valve preferably permits inflow of the molten metal into the piston cavity. Additionally, during the downstroke of the piston, the inlet to the check valve preferably remains located sufficiently below the metal oxide film surface of the molten metal in the holder furnace such that the metal oxide film surface remains substantially undisturbed during pumping of the molten metal from the holder furnace to the mold cavity.

[0012] The injector may further include a lifting mechanism positioned above the metal oxide film surface when the holder furnace contains the molten metal. The lifting mechanism may be operatively connected to the piston for moving the piston through the downstroke and the return stroke. The lifting mechanism may be a rack and pinion.

[0013] The cylinder may further define a fill conduit in fluid communication with the piston cavity through a top wall of the cylinder. The fill conduit preferably extends along an axis substantially parallel to the piston. The fill conduit may be in fluid communication with the mold cavity through a fill tube passing through the bottom side of the mold. The molten metal received in the piston cavity may be pumped upward into the fill conduit and the fill tube by the piston during the return stroke of the piston for injecting the molten metal into the mold cavity under pressure. A source of inert gas may be in fluid communication with the mold cavity such that during the downstroke of the piston, the piston cavity is filled with inert gas flowing down the fill tube and the fill conduit, which substantially prevents the formation of metal oxides in the piston cavity. Preferably, the piston and the cylinder are made of a material compatible with molten aluminum alloys.

[0014] Further details and advantages of the present invention will become apparent from the following detailed description in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a cross-sectional view of a molten metal injector system in accordance with the present invention;

[0016]FIG. 2 is a cross-sectional view of an injector for the molten metal injector system of FIG. 1 according to the present invention;

[0017]FIG. 3 is a cross-sectional view of the injector of FIG. 2 which incorporates a molten metal filter; and

[0018]FIG. 4 is a side view of the molten metal injector system of FIG. 1 having multiple injectors in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0019]FIG. 1 shows a molten metal injector system in accordance with the present invention and designated with reference numeral 10. The injector system 10 generally includes a holder furnace 12 that contains a supply of molten metal 14, such as molten aluminum alloy, a casting mold 16 positioned above the holder furnace 12, and at least one injector 18 supported from the casting mold 16. The molten metal 14 contained in the holder furnace 12 may be exposed to the atmosphere and, as a result, a metal oxide film surface 20 forms at the top of the molten metal 14 contained in the holder furnace 12. Alternatively, the holder furnace 12 may further include a cover (not shown) such that the molten metal 14 is enclosed within the holder furnace 12. The holder furnace 12 is in fluid communication with a main melter furnace 22, which typically contains a large quantity of the molten metal 14 while the holder furnace 12 contains a much smaller quantity of molten metal 14. For example, the main melter furnace 22 may contain 30,000 pounds of the molten metal 14 while the holder furnace 12 may contain about 2,000 pounds of the molten metal 14. The main melter furnace 22 maintains a steady supply of the molten metal 14 to the holding furnace 12 during operation of the injector system 10. When the molten metal 14 is a containment-difficult molten metal, such as molten aluminum alloys, the holder furnace 12 is preferably lined with refractory material 24 such as Sigma or BETA II castable refractory material products manufactured by Permatech.

[0020] The casting mold 16 is supported by a support surface 26, such as the platform, i.e., the lower platen, of a casting machine. The casting mold 16 is configured for casting ultra large, thin-walled components such as those that may be used in ground transportation vehicles. An ultra large, thin-walled component part for a ground transportation vehicle may have dimensions approaching 3 meters long, 1.7 meters wide and 0.4 meters in depth, and the casting mold 16 would be configured accordingly. The casting mold 16 is preferably suitable for use with molten metal alloys having a low melting point, such as aluminum alloys. The casting mold 16 includes a holder frame 28 that is supported on the support surface 26. The support surface 26 is located a sufficient distance above the holder furnace 12 so that at least a portion of the injector 18 lies above the metal oxide film surface 20 of the molten metal 14 contained in the holder furnace 12. For example, the support surface 26 and, hence, the casting mold 16 may be eighteen inches above the metal oxide film surface 20 of the molten metal 14 when the holder furnace 12 is filled with the molten metal 14 in a preferred embodiment of the present invention. The casting mold 16 generally includes a lower die 30 and an upper die 32 which together define a mold cavity 34. A cover plate 36 is positioned on top of the upper die 32. A top clamp plate 38 is separated from the cover plate 36 by a spacer block 40. Hoist rings 42 are preferably attached to the top clamp plate 3 8 for mold removal and installation. A bottom side 44 of the casting mold 16 faces the holder furnace 12. The upper die 32 is connected to the upper platen of the casting mold 16. After casting a part, the upper mold 32 is raised with the part retained in the upper mold 32. When the casting mold 16 is fully open and a means are provided to catch the part, the part is ejected from the upper mold 32.

[0021] In a preferred embodiment of the present invention, a plurality of the injectors 18 is supported from the bottom side 44 of the casting mold 16 and projects downward into the holder furnace 12. However, in FIG. 1 only one injector 18 is shown for clarity and expediency in explaining the present invention. An arrangement of the present invention utilizing a plurality of the injectors 18 is shown in FIG. 4. Each of the injectors 18 shown in FIG. 4 is identical to the injector 18 shown in FIGS. 1 and 3 as discussed hereinafter.

[0022] FIGS. 1-3 show the details of the injector 18 according to the present invention. The injector 18 includes a cylinder 46 for submerging in the molten metal 14 contained in the holder furnace 12. The cylinder 46 defines a piston cavity 48 and a fill conduit 50 in fluid communication with the piston cavity 48. The cylinder 46 includes a lower end 52 that is fully submerged in the molten metal 14 contained in the holder furnace 12 when the holder furnace 12 is filled with the molten metal 14. At the lower end 52 of the cylinder 46, the cylinder 46 may define a tapered inner surface 54. The cylinder 46 is generally defined by a sidewall 56 having an inner surface 57.

[0023] A piston 58 is positioned and movable within the piston cavity 48. The piston 58 has substantially the same diameter as the piston cavity 48. The tapered inner surface 54 generally has a slightly larger diameter than the piston 58. The piston 58 is movable in a reciprocating manner within the piston cavity 48, i.e., through a downstroke and a return stroke. FIG. 2 illustrates the piston 58 at a substantially full downstroke position in solid lines, and illustrates a full return stroke position of the piston 58 in broken lines. At the substantially full downstroke position of the piston 58, the piston 58 preferably remains in contact with the inner surface 57 of the cylinder 46 and prevents inflow of the molten metal 14 into the piston cavity 48 through the lower end 52 of the cylinder 46. The total vertical distance the piston 58 extends downward may be controlled by a PLC (Programmable Logic Controller), which controls servomotors powering a lifting mechanism attached to the piston 58, as discussed hereinafter.

[0024] The cylinder 46 and the piston 58 are preferably made of a material compatible with molten aluminum alloys. In particular, suitable materials for the cylinder 46 and the piston 58 include graphite and high quality ceramic compounds such as Sialon and Si₃N₄. Additionally, other suitable materials compatible with molten aluminum alloys include blends of ZrO₂ and BN. Further, the present invention envisions the use of both graphite and high quality ceramic compounds for the cylinder 46 and the piston 58. Generally, all components of the injector 18 that come in contact with molten aluminum alloys are made of materials compatible with molten aluminum alloys as outlined above.

[0025] Preferably, as shown in FIG. 1, the piston 58 and the cylinder 40 are oriented substantially perpendicular to the bottom side 44 of the casting mold 16. Hence, during the downstroke of the piston 58, the piston 58 moves in a direction away from the bottom side 44 of the casting mold 16, and during the return stroke the piston 58 moves upward toward the bottom side 44 of the casting mold. In particular, the fill tube 61 extends through a vertical opening in the holder frame 28 and the lower die 30. The fill tube 61 and fill conduit 50 place the piston cavity 48 in fluid communication with the mold cavity 34. The fill tube 61 may be made of materials similar to those used for the cylinder 46 and the piston 58.

[0026] The piston 58 is movable through its downstroke and return stroke by a lifting mechanism 64 that is fixed to the cylinder 46 by the connecting flange 62. The connecting flange 62, as stated previously, is also used to connect the fill tube 61 to the fill conduit 50. The lifting mechanism 64 is preferably a rack and pinion as shown in the figures, but may also be a chain drive, or another similar mechanical device. With the cylinder 46 substantially submerged in the molten metal 14 contained in the holding furnace 12, the lifting mechanism 64 is located above the metal oxide film surface 20 of the molten metal 14. In particular, the lifting mechanism 64 is preferably located about fourteen inches above the metal oxide film surface 20 of the molten metal 14 contained in the holder furnace 12 when the holder furnace 12 contains the molten metal 14 in a preferred embodiment of the present invention. The lifting mechanism 64 and, hence, the injector 18 are fixed to the bottom side 44 of the casting mold 16 by an upper flange 66. The lifting mechanism 64 may be connected to the upper flange 66 by mechanical fasteners, i.e., bolts. Similarly, the upper flange 66 may be fixed to the bottom side 44 of the casting mold 16 by mechanical fasteners, i.e., bolts. Thus, the injector 18 is attached to the lower die 30 of the casting mold 16 via the flange 66 and structural connections between the flange 66 and the connecting flange 62.

[0027] Due to the close proximity of the lifting mechanism 64 to the holder furnace 12, the lifting mechanism 64 is subjected to high temperatures and is preferably made of a material capable of withstanding temperatures on the order of 600-1000° F. Suitable materials for the lifting mechanism 64 include those previously discussed that are compatible with molten aluminum alloys as well as steel and other ferrous materials since the lifting mechanism 64 does not directly contact the molten metal 14 contained in the holder furnace 12. The rack and pinion, which forms the lifting mechanism 64, may be driven by a remotely controlled servomotor 67. The servomotor may be controlled by a PLC 77 which has been programmed to adjust the vertical distance the piston 58 travels during its downstroke, as will be appreciated by those skilled in the art. For example, the lifting mechanism 64 controlling the piston 58 may be set to allow the piston 58 to form a gap with the tapered inner surface 54 of the cylinder 46, which permits any molten metal contained in the piston cavity 48 to drain from the piston cavity 48 when it is time to perform routine maintenance on the injector 18 or replace the injector 18.

[0028] Referring now, in particular, to FIGS. 1 and 2, the piston 58 defines a molten metal intake 68, i.e., an aperture, for receiving the molten metal 14 contained in the holder furnace 12 into the piston cavity 48. The piston 58 preferably further includes a check valve 69 positioned in the molten metal intake 68, which permits one-way flow of the molten metal 14 into the piston cavity 48. The piston 58 is preferably located within the cylinder 46 such that with the cylinder 46 at least partially submerged in the molten metal 14 contained in the holding furnace 12, the piston 58 remains submerged in the molten metal 14 contained in the holder furnace 12 and, thus, in an area of clean molten metal flow. Hence, the molten metal intake 68 and the check valve 69 also remain submerged in the molten metal 14. Thus, the molten metal intake 68 and the check valve 69 are always located below the metal oxide film surface 20 of the molten metal 14. In particular, with the piston 58 in the substantially full downstroke position, the top of the piston 58 is about eight inches below the metal oxide film surface 20 of the molten metal 14 in a preferred embodiment of the injector 18 of the present invention.

[0029] The molten metal intake 68 and the check valve 69 permit fluid communication between the piston cavity 48 and the holder furnace 12. The check valve 69 is configured to permit inflow of the molten metal 14 from the holder furnace 12 during the downstroke of the piston 58, and to prevent inflow to the piston cavity 48 during the return or pumping stroke of the piston 58. Hence, the check valve 69 opens for inflow of the molten metal 14 when the piston 58 begins its downstroke and prevents inflow when the piston 58 reaches its substantially full downstroke piston and begins its return stroke. The check valve 69 is preferably a ball check valve. The ball check valve 69 may be constructed using high quality ceramic compounds such as Sialon and Si₃N₄ or other suitable material compatible with molten aluminum alloy including blends of ZrO₂ and BN, and other materials as discussed previously. The ball valve seat of the ball check valve 69 can either be formed integral in the piston 58 or be a separate insert.

[0030] A molten metal filter 70, as shown in FIG. 3, may be used to cover an inlet 71 to the check valve 69 to filter and remove debris from the molten metal 14 flowing into the piston cavity 48 through the check valve 69. In addition to molten metal filtration, the molten metal filter 70 may regulate the flow of molten metal 14 into the piston cavity 48 so that there is no initiation of turbulent molten metal flow into the piston cavity 48. The area of the molten metal filter 70 is generally much larger than the flow area without a filter to avoid impeding molten metal flow into the piston cavity 48. Thus, the area of the molten metal filter 70 is large in comparison to the inlet 71 to the check valve 69.

[0031] Referring now to FIGS. 1-3, operation of the injector 18 through a downstroke and return stroke cycle of the piston 58 will now be discussed. As stated previously, the injector 18 is supported from the bottom side 44 of the casting mold 16. The cylinder 46 and the piston 58 are substantially submerged in the molten metal 14 contained in the holding furnace 12. As the piston 58 begins its downstroke, the check valve 69, preferably a ball check valve, located within the molten metal intake 68 permits the molten metal 14 to flow into the piston cavity 48. As the piston 58 moves through its downstroke, the molten metal 14 continues to flow into the piston cavity 48 through the check valve 69 and the molten metal filter 70, if present. At the substantially full downstroke position of the piston 58, the check valve 69 closes and prevents further inflow. The time necessary for the piston 58 to reach its substantially full downstroke position may be set to allow the piston cavity to fully fill with the molten metal 14 as the piston 58 reaches its substantially full downstroke position. The rate of inflow of the molten metal 14 is preferably controlled so that there is no initiation of turbulent molten metal flow into the piston cavity 48, which substantially reduces the likelihood of forming metal oxides in the piston cavity 48. The PLC 77 controlling the servomotors 67 driving the lifting mechanism 64 may control the piston 58, as will be appreciated by those skilled in the art. The lifting mechanism 64 reverses the direction of the piston 58 when the piston 58 reaches its substantially full downstroke position and has been signaled to begin the return stroke. The lifting mechanism 64 causes the piston 58 to begin moving upward through its return stroke. The PLC 77 controlling the servomotors 67 of the lifting mechanism 64 provides flexibility in operating the injector 18 of the present invention. For example, the piston 58 may be controlled such that the piston cavity 48 is entirely filled with molten metal 14 flowing through the molten metal intake 68 and the check valve 69 before the piston 58 reaches its substantially full downstroke position.

[0032] Once the piston 58 reaches its substantially full downstroke position, a casting cycle of the system 10 is ready to commence. At the substantially full downstroke position of the piston 58, the check valve 69 prevents further inflow to the piston cavity 48, and the piston cavity 48 is typically completely filled with molten metal 14. The lifting mechanism 64 is engaged by the PLC 77 controlling the servomotors 67 driving the lifting mechanism 64 to begin the injection stroke (i.e., return stroke) of the piston 58. This follows a pre-specified position versus time path. When the molten metal 14 fills the mold cavity 34, pressure builds and the servomotors 67 can no longer follow the predetermined position versus time relation and the PLC 77 abruptly changes the servomotors to a torque holding condition. After the torque holding condition is established, which reflects a pressure intensification of about 5 to 45 psi for a sufficient time for the molten metal 14 to solidify in the mold cavity 34, the piston 58 is then slowly lowered to the start position (i.e., downstroke position) and the check valve 69 again permits inflow of the molten metal 14 from the holder furnace 12 into the piston cavity 48. As stated previously, the piston 58 may be set to travel any vertical distance required at any predetermined rate and is not specifically limited to traveling between the downstroke and return stroke positions shown in FIGS. 2 and 3.

[0033] As the piston 58 moves upward through its return stroke, the molten metal 14 now contained in the piston cavity 48 is pumped upward by the piston 58 from the holder furnace 12. The molten metal 14 follows a path through the fill conduit 50 and into the fill tube 61. The molten metal 14 in the fill conduit 50 and the fill tube 61 is injected under low-pressure (i.e., less than about 15 psi) into the mold cavity 34. As the piston 58 reaches its full return stroke position, for example, the lifting mechanism 64 is stopped. The piston 58 may be stopped prior to the full return stroke position if a torque holding condition occurs indicating that the mold cavity 34 is filled with the molten metal 14. The PLC 77 continually monitors this torque holding condition and the PLC commands are based upon this information. If desired, the injector 18 may be manually remotely controlled.

[0034] The injector 18 of the present invention advantageously locates the molten metal intake 68 and the check valve 69 located therein well below the metal oxide film surface 20 of the molten metal 14. Since the molten metal intake 68 for the injector 18 is located below the metal oxide film surface 20, the metal oxide film surface 20 remains substantially undisturbed as the molten metal 14 from the holder furnace 12 flows into the piston cavity 48 through the molten metal intake 68 and the check valve 69. The molten metal intake 68 always remains in an area of clean molten metal flow. This assures that disturbances to the metal oxide film surface 20 are minimized and substantially prevents metal oxides from being introduced into the piston cavity 48 from the metal oxide film surface 20.

[0035] In addition, because the piston cavity 48 is filled during the downstroke of the piston 58 via the molten metal intake 68 and the check valve 69, this helps prevent the initiation of turbulent molten metal flow and thus formation of metal oxides in the piston cavity 48 due to the action of the piston 58. A known disadvantage with many prior art piston arrangements is that the pumping stroke of the piston is generally during the downstroke which has a tendency to disturb the metal oxide film surface of the supply of molten metal in which the piston operates, as well as create disturbances within the piston cavity which could cause metal oxides to form in the piston cavity. In the injector 18, the pumping stroke is the return stroke, which minimizes the chances of forming metal oxides in the piston cavity 48, as well as minimizes the disturbances to the metal oxide film surface 20 of the molten metal 14 in the holder furnace 12. Furthermore, the check valve 69 permits the inflow of the molten metal 14 into the piston cavity 48 only during the downstroke of the piston 58, which substantially prevents a vacuum from being generated in the piston cavity 48 that could pull atmospheric air into the fill tube 61, the fill conduit 50 and further down into the piston cavity 48, which could possibly lead to the formation of metal oxides in the piston cavity 48.

[0036] As shown in FIGS. 1 and 4, the injector 18 of the present invention may further include a source of inert gas 80, such as argon or nitrogen, in fluid communication with the mold cavity 34. The source of inert gas 80 preferably supplies the inert gas through the lower die 30 or the upper die 32 and into the mold cavity 34. The inert gas 80 will flow down the fill tube 61, the fill conduit 50 and into the piston cavity 48 during operation of the injector 18. The inert gas substantially prevents the introduction of atmospheric air into the fill tube 61, the fill conduit 50 and the mold cavity 34 which could potentially form metal oxides in the piston cavity 48. As stated previously, the present invention envisions the use of a plurality of injectors 18 suspended from the bottom side 44 of the casting mold 16, as show in FIG. 4. The plurality of injectors 18 shown in FIG. 4 is supported from the bottom side 44 of the mold 16 to optimize the inflow of the molten metal 14 into the mold cavity 34. The injectors 18 may be individually controlled by a PLC (not shown), for example, such that the injectors 18 inject the molten metal 14 from the holder furnace 12 at different rates and at different times as necessary to fill the mold cavity 34 to form the component.

[0037] The injector system of the present invention provides a simplified apparatus and method for casting inexpensive, but high quality thin-walled components. The injector system of the present invention may be applied to cast complex components as a single piece, which could be used to replace stamping assemblies made from multiple stamped components. In addition, the injector system of the present invention includes a piston which pumps molten metal during its return stroke and provides a conduit for direct inflow of molten metal into the piston cavity during the downstroke of the piston. Consequently, the molten metal intake in the injector system of the present invention is generally located substantially below the metal oxide film surface of the molten metal, which means that the metal oxide film surface of the molten metal remains substantially undisturbed during operation of the injector of the system.

[0038] While the preferred embodiments of the present invention were described herein, various modifications and alterations of the present invention may be made without departing from the spirit and scope of the present invention. The scope of the present invention is defmed in the appended claims and equivalents thereto. 

What is claimed is:
 1. An injector for injecting molten metal into a mold cavity of a casting mold, comprising: a cylinder for at least partially submerging in a supply of molten metal, with the cylinder defining a piston cavity, and with the cylinder defining a fill conduit in fluid communication with the piston cavity and extending through a top wall of the cylinder; a piston positioned within the piston cavity and movable through a downstroke and a return stroke, with the piston defining a molten metal intake for receiving molten metal into the piston cavity; and a lifting mechanism fixed to the cylinder and operatively connected to the piston for moving the piston through the downstroke and the return stroke, wherein the fill conduit extends along an axis substantially parallel to the piston.
 2. The injector of claim 1, further including a check valve positioned in the molten metal intake defined by the piston, with the check valve having an inlet for receiving molten metal into the piston cavity when the cylinder and piston are at least partially submerged in molten metal.
 3. The injector of claim 2, wherein the check valve is a ball check valve.
 4. The injector of claim 2, wherein the check valve is configured to permit inflow of molten metal into the piston cavity during the downstroke of the piston when the cylinder and piston are at least partially submerged in molten metal, and wherein the check valve is configured to prevent inflow of molten metal into the piston cavity during the return stroke of the piston when the cylinder and piston are at least partially submerged in molten metal.
 5. The injector of claim 2, further including a molten metal filter covering the inlet to the check valve.
 6. The injector of claim 1, wherein the piston and the cylinder are made of materials compatible with molten aluminum and molten aluminum alloys.
 7. The injector of claim 1, wherein the lifting mechanism is a rack and pinion. 